linux-kernel - Re: [PATCH v2] USB: gadget: Add ID numbers to configfs-gadget driver names

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Message-ID: <56b0f4ad-9194-eb20-cffd-79c57171163b@amperemail.onmicrosoft.com>
Date:   Fri, 30 Dec 2022 17:29:57 +0700
From:   Chanh Nguyen <chanh@...eremail.onmicrosoft.com>
To:     Andrzej Pietrasiewicz <andrzej.p@...labora.com>,
        Chanh Nguyen <chanh@...amperecomputing.com>,
        OpenBMC Maillist <openbmc@...ts.ozlabs.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Frank Li <frank.li@....com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Dan Vacura <w36195@...orola.com>,
        Jakob Koschel <jakobkoschel@...il.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Vijayavardhan Vennapusa <vvreddy@...eaurora.org>,
        Rondreis <linhaoguo86@...il.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Open Source Submission <patches@...erecomputing.com>
Subject: Re: [PATCH v2] USB: gadget: Add ID numbers to configfs-gadget driver
 names



On 22/12/2022 22:20, Andrzej Pietrasiewicz wrote:
> Hi,
> 
> W dniu 21.12.2022 o 10:13, Chanh Nguyen pisze:
>> It is unable to use configfs to attach more than one gadget. When
>> attaching the second gadget, it always fails and the kernel message
>> prints out:
>>
>> Error: Driver 'configfs-gadget' is already registered, aborting...
>> UDC core: g1: driver registration failed: -16
>>
> 
> I assume you are interested in a scenario where there is more than one
> UDC available which means you can have more than one active gadget?
> 

Yes, I'd like to have more active gadgets. For example, mass_storage and 
ecm usb, ...

>> This commit fixes the problem by a ".N" suffix added to each
>> configfs_gadget's driver name (where N is a unique ID number),
>> thus making the names distinct.
>>
>> Fixes: fc274c1e9973 ("USB: gadget: Add a new bus for gadgets")
>> Signed-off-by: Chanh Nguyen <chanh@...amperecomputing.com>
>>
>> ---
>> Changes in v2:
>>    - Replace scnprintf() by kasprintf() to simplify the code [CJ]
>>    - Move the clean up code from gadgets_drop() to
>>      gadget_info_attr_release()                        [Frank Li]
>>    - Correct the resource free up in gadges_make()   [Alan Stern]
>>    - Remove the unnecessary variable in gadgets_make()    [Chanh]
>>    - Fixes minor grammar issue in commit message          [Chanh]
>> ---
>>   drivers/usb/gadget/configfs.c | 25 ++++++++++++++++++++++++-
>>   1 file changed, 24 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/gadget/configfs.c 
>> b/drivers/usb/gadget/configfs.c
>> index 96121d1c8df4..7faf68bfa716 100644
>> --- a/drivers/usb/gadget/configfs.c
>> +++ b/drivers/usb/gadget/configfs.c
>> @@ -3,6 +3,7 @@
>>   #include <linux/module.h>
>>   #include <linux/slab.h>
>>   #include <linux/device.h>
>> +#include <linux/idr.h>
>>   #include <linux/kstrtox.h>
>>   #include <linux/nls.h>
>>   #include <linux/usb/composite.h>
>> @@ -11,6 +12,8 @@
>>   #include "u_f.h"
>>   #include "u_os_desc.h"
>> +static DEFINE_IDA(driver_id_numbers);
>> +
>>   int check_user_usb_string(const char *name,
>>           struct usb_gadget_strings *stringtab_dev)
>>   {
>> @@ -52,6 +55,9 @@ struct gadget_info {
>>       char qw_sign[OS_STRING_QW_SIGN_LEN];
>>       spinlock_t spinlock;
>>       bool unbind;
>> +
>> +    /* Make driver names unique */
>> +    int driver_id_number;
>>   };
>>   static inline struct gadget_info *to_gadget_info(struct config_item 
>> *item)
>> @@ -393,6 +399,8 @@ static void gadget_info_attr_release(struct 
>> config_item *item)
>>       WARN_ON(!list_empty(&gi->string_list));
>>       WARN_ON(!list_empty(&gi->available_func));
>>       kfree(gi->composite.gadget_driver.function);
>> +    kfree(gi->composite.gadget_driver.driver.name);
>> +    ida_free(&driver_id_numbers, gi->driver_id_number);
>>       kfree(gi);
>>   }
>> @@ -1623,13 +1631,28 @@ static struct config_group *gadgets_make(
>>       gi->composite.gadget_driver = configfs_driver_template;
>> +    gi->driver_id_number = ida_alloc(&driver_id_numbers, GFP_KERNEL);
>> +    if (gi->driver_id_number < 0)
>> +        goto err;
>> +
>> +    gi->composite.gadget_driver.driver.name = kasprintf(GFP_KERNEL,
>> +                                "configfs-gadget.%d",
>> +                                gi->driver_id_number);
> 
> I'm wondering if it maybe makes more sense to use the gadget name as a 
> suffix
> instead?
> 
>      gi->composite.gadget_driver.driver.name =
>          kasprintf(GFP_KERNEL, "configfs-gadget.%s" name);
> 
> So that when you
> 
> mkdir g1
> 
> you will ultimately see /sys/bus/gadget/drivers/configfs-gadget.g1
> 
> instead of /sys/bus/gadget/drivers/configfs-gadget.0
> 
> Gadget names are guaranteed to be unique because they are created
> as sibling subdirectories in configfs. Your patch would then be greatly
> simplified (no need for ida).
> 
> Regards,
> 
> Andrzej
> 

Thanks, Andrzej! I'll update that in patch v3

>> +    if (!gi->composite.gadget_driver.driver.name)
>> +        goto out_free_driver_id_number;
>> +
>>       gi->composite.gadget_driver.function = kstrdup(name, GFP_KERNEL);
>>       gi->composite.name = gi->composite.gadget_driver.function;
>>       if (!gi->composite.gadget_driver.function)
>> -        goto err;
>> +        goto out_free_driver_name;
>>       return &gi->group;
>> +
>> +out_free_driver_name:
>> +    kfree(gi->composite.gadget_driver.driver.name);
>> +out_free_driver_id_number:
>> +    ida_free(&driver_id_numbers, gi->driver_id_number);
>>   err:
>>       kfree(gi);
>>       return ERR_PTR(-ENOMEM);
>